Martínez-Ovalle S A, Barquero R, Gómez-Ros J M, Lallena A M
Departamento de Física, Universidad Pedagógica y Tecnológica de Colombia, Tunja, Colombia.
Radiat Prot Dosimetry. 2011 Nov;147(4):498-511. doi: 10.1093/rpd/ncq501. Epub 2011 Jan 12.
In this work, the dose equivalent due to photoneutrons and the neutron spectra in tissue was calculated for various linacs (Varian Clinac 2100C, Elekta Inor, Elekta SL25 and Siemens Mevatron KDS) operating at energies between 15 and 20 MV, using the Monte Carlo code MCNPX (v. 2.5). The dose equivalent in an ICRU tissue phantom has been calculated for anteroposterior treatments with a detailed simulation of the geometry of the linac head and the coupled electron-photon-neutron transport. Neutron spectra at the phantom entrance and at 1-cm depth in the phantom, depth distribution of the neutron fluence in the beam axis and dose distributions outside the beam axis at various depths have also been calculated and compared with previously published results. The differences between the neutron production of the various linacs considered has been analysed. Varian linacs show a larger neutron production than the Elekta and Siemens linacs at the same operating energy. The dose equivalent due to neutrons produced by medical linacs operating at energies >15 MeV is relevant and should not be neglected because of the additional doses that patients can receive.
在这项工作中，使用蒙特卡罗代码MCNPX（版本2.5），针对能量在15至20 MV之间运行的各种直线加速器（瓦里安Clinac 2100C、医科达Inor、医科达SL25和西门子Mevatron KDS），计算了组织中光中子产生的剂量当量和中子能谱。通过对直线加速器机头几何结构以及耦合的电子 - 光子 - 中子输运进行详细模拟，计算了ICRU组织模体中前后向治疗的剂量当量。还计算了模体入口处和模体中1 cm深度处的中子能谱、束轴上中子注量的深度分布以及不同深度处束轴外的剂量分布，并与先前发表的结果进行了比较。分析了所考虑的各种直线加速器中子产生的差异。在相同运行能量下，瓦里安直线加速器的中子产生量比医科达和西门子直线加速器更大。能量大于15 MeV的医用直线加速器产生的中子所导致的剂量当量是相关的，且由于患者可能接受的额外剂量，不应被忽视。
